Are Your Seeds Still Good? Find Out With This Simple Trick

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Most gardeners keep a stash of seedsthat they carry over from year to year. It can be a very cost effective way of planting vegetables and flowers, but there’s a catch: seeds have shelf life. Over time they lose their viability, making planting them a potential waste of your time. There’s nothing worse than prepping soil, thoughtfully planting, and carefully watering for weeks only to end up with duds. Luckily, there are two fast and easy ways to determine if your seeds are still viable before you even pick up a trowel. 

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Method 1: The Flashlight Candling Test

Candling is a technique people have used for centuries to determine if bird eggs are fertilized. Basically, it involves holding a flashlight up to an egg in a dark room. If the egg is opaque, the embryo is healthy. If it’s translucent, the egg is no longer viable. The process works the same with a bag of seeds. 

• The Test: Hold the bag up to a flashlight, (your smartphone light will do) in a dark room. 
• The Result: If the seed looks dark and opaque, it’s healthy. If it looks hollow, the embryo has shriveled and died. 
• Best For: Since this test involves looking through the shell, it works best with larger seeds, like beans, peas, squash, cucumber, and corn.

Why it Works

A viable seed is packed with energy called endosperm, which it uses to fuel its growth when the sprout emerges from the seed shell. As the seed ages sitting in your shed or garage, the energy source begins to dry up and shrink, creating air gaps inside the shell. By shining a light on the shell, you’re illuminating those gaps, revealing its hollow interior. 

Method 2: The Paper Towel “Sprout” Test

With smaller sees, light won’t tell you whether they’re viable or not. You’ll need to conduct a brief laboratory style germination test instead.

1. Preparation: Dampen a paper towel then place 10 seeds in a straight line on one half of the towel
2. Seal the Seeds: Fold the paper towel over, then slip it inside of a Ziploc bag and leave it slightly unzipped for air. 
3. Wait: Place the bag in a warm spot, such as on top of your fridge, for about a week. 
4. Evaluate: Count the sprouts to determine the seed condition:

• If 9 or 10 seeds sprout, you have 90 to 100 percent seed viability. Go ahead and plant the seed. 
• If 5 sprout, you have 50 percent viability. Plant twice as many seeds per hole. 
• If less than 3 sprouted, they aren’t worth planting. Discard the seed packet 

Why Do Seeds Go Bad?

Seeds fail as a result of exposure to heat, light, and moisture while they’re in storage. You can preserve seeds by placing the seed packets in a glass jar with a silica packet (like the ones you find in shoe boxes) and storing them in a cool dry place, like the back of your pantry.